1. Field of the Invention
The present invention relates to an image pickup apparatus and driving method therefor, and more particularly, to an image pickup apparatus and driving method therefor, capable of focus detection based on a pupil division method.
2. Description of the Related Art
Recently, solid-state image pickup elements used for image pickup apparatuses such as digital still cameras and digital video cameras have been growing in functionality.
Japanese Patent Application Laid-Open No. 2001-124984 discloses a technique capable of focus detection based on a pupil division method in relation to an image pickup element. According to Japanese Patent Application Laid-Open No. 2001-124984, each pixel of the image pickup element has two photodiodes, which are configured to receive, by means of a single microlens, light passing through respective different pupils of a photographing lens. Thus, the photographing lens can detect focus by comparing output signals from the two photodiodes. Also, by adding the output signals from the two photodiodes, a signal of a normal photographing image can be obtained.
On order to perform focus detection by using an image pickup element in which each pixel contains two photodiodes in the case of Japanese Patent Application Laid-Open No. 2001-124984, a signal needs to be acquired from each of the two photodiodes. Consequently, if focus detection signals are to be obtained in an entire pixel area, the quantity of signals to be read out increases two-fold compared to a conventional image pickup element in which each pixel contains a single photodiode, substantially increasing a read-out time.